Simple energy-budget model for yolk-feeding stages of Atlantic cod (Gadus morhua)

Atlantic cod (Gadus morhua) is a commercially important species, and therefore, understanding the influence of environmental factors and anthropogenic stressors on its early life stages is of considerable relevance. In this contribution, we apply a simple and generic energy-budget framework (DEBkiss) to data for the yolk-feeding stages of cod. The model is capable of explaining the changes in yolk volume, dry weight, oxygen use and body length, simultaneously with a small number of parameters. The calibrated model was subsequently successfully tested with other data sets. Interestingly, the light conditions after hatching affect growth and respiration rates, which is traced to a change in the maintenance costs (linked to swimming activity). Despite the satisfactory performance of the model, several uncertainties remain. Especially the bioenergetics around the point of complete yolk absorption require further attention, which is complicated by the fact that the behaviour around this point differed between data sets. The presented model can be used for exploring effects of stressors on early-life stages of cod, and likely for other aquatic egg-laying species as well.